Electrospray Mass Spectrometer Research Articles

Sphingolipidomic profiling of human Dental Pulp Stem Cells undergoing osteogenic differentiation

It is now recognized that sphingolipids are involved in the regulation and pathophysiology of several cellular processes such as proliferation, migration, and survival. Growing evidence also implicates them in regulating the behaviour of stem cells, the use of which is increasingly finding application in regenerative medicine. A shotgun lipidomic study was undertaken to determine whether sphingolipid biomarkers exist that can regulate the proliferation and osteogenic differentiation of human Dental Pulp Stem Cells (hDPSCs). Sphingolipids were extracted and identified by direct infusion into an electrospray mass spectrometer. By using cells cultured in osteogenic medium and in medium free of osteogenic stimuli, as a control, we analyzed and compared the SPLs profiles. Both cellular systems were treated at different times (72 hours, 7 days, and 14 days) to highlight any changes in the sphingolipidomic profiles in the subsequent phases of the differentiation process. Signals from sphingolipid species demonstrating clear differences were selected, their relative abundance was determined, and statistical differences were analyzed. Thus, our work suggests a connection between sphingolipid metabolism and hDPSC osteogenic differentiation and provides new biomarkers for improving hDPSC-based orthopaedic regenerative medicine.

A Comparative Analysis between the Phenolic Content, Key Enzyme Inhibitory Potential, and Cytotoxic Activity of Arum italicum Miller in Two Different Organs

The present study assessed two different plant parts (leaves and tubers) of Arum italicum species growing in Northeast Algeria for their phytochemical composition and pharmacological effects. The phytochemical content was determined using ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS). The results revealed that the tuber extract was rich in lignans with a fraxiresinol glycoside as the major compound. In contrast, the leaf extract was rich in flavonoid glycosides, described for the first time in the aerial part of this species. The extract’s inhibitory activity against key enzymes was linked to hyperglycemia, α-glucosidase, and α-amylase, and their ability to inhibit the growth of human gastric carcinoma (AGS) and lung carcinoma (A549) cancer cell lines was also assessed. A cell line morphology study was also conducted with the most effective extract. The chromatin status of the cells was evaluated using DAPI, while the cytoplasmic morphology was evaluated using phalloidin. The tuber extract generally inhibited α-glucosidase and α-amylase enzymes more efficiently than the leaf extract. Its inhibition effect against the α-glucosidase was significantly higher when compared to the standard acarbose. The tuber extract also caused more viability loss of AGS and A549 cancer cells than the leaf extract in the cytotoxicity assay. In conclusion, our findings show that, compared to the leaf extract, the tuber extract exhibited more pronounced biological effects. The strong inhibitory potential of the tuber extract against the α-glucosidase enzyme should also be highlighted, which suggests it is a good candidate for discovering new antidiabetic agents.

Statistical Medium Optimization for the Production of Anti-Methicillin-Resistant Staphylococcus aureus Metabolites from a Coal-Mining-Soil-Derived Streptomyces rochei CMB47

The development of novel antibacterial drugs needs urgent action due to the global emergence of antibiotic resistance. In this challenge, actinobacterial strains from arid ecosystems are proving to be promising sources of new bioactive metabolites. The identified Streptomyces rochei strain CMB47, isolated from coal mine Saharan soil, provided an ethyl acetate extract which tested against a series of pathogens. It displayed a minimum inhibitory concentration of <0.439 µg/mL against MRSA. A statistical experimental design using a response surface methodology (RSM) based on the second-order rotatable central composite design (RCCD) was planned to develop an efficient fermentation process able to improve the bioactive metabolite production. The optimal conditions were determined for starch and NaNO3 concentrations, incubation time and the initial pH value, reaching the inhibition zone diameter of 20 mm, close to the experimental value, after validation of the model. A bioassay-guided fractionation of the crude extract provided the most active fractions, which were analyzed by HPLC equipped with a photodiode array detector and coupled online with an electrospray mass spectrometer (HPLC-DAD/ESI-MS), obtaining preliminary indications on the molecular structures of the metabolites. These results support the potential interest in further investigations into the purification and full characterization of the metabolites responsible for the biological activity observed so far.

Winery By-Products as Sources of Bioactive Tryptophan, Serotonin, and Melatonin: Contributions to the Antioxidant Power.

The amino acid tryptophan and its derived molecules serotonin and melatonin are involved in a wide range of physiological functions that contribute significantly to human health, namely antioxidant, immune-active, and neurological properties. Grapes and wine are a source of these compounds, but their presence in wine by-products remains underexplored. Therefore, the aim of this work was the identification and quantification of tryptophan, serotonin, and melatonin in winery by-products (grape stems, grape pomace, and wine lees) by ultra-high performance liquid chromatography coupled to electrospray ionization and mass spectrometer with triple-quadrupole technology (UHPLC-ESI-QqQ-MS/MS), as well as the evaluation of the extracts obtained (by applying specific extraction conditions for each of them) for their antioxidant and reducing capacity (by three different and complementary methods: FRAP, ABTS•+, and ORAC). Furthermore, correlation analyses were developed to establish the contribution of the different analytes to the total antioxidant activity. The main results obtained pointed out grape stems as the by-product with the highest tryptophan content (96.28 mg/kg dw) and antioxidant capacity (142.86, 166.72, and 363.24 mmol TE/kg dw, FRAP, ABTS•+, and ORAC, respectively), while serotonin and melatonin were the predominant derivatives in grape pomace (0.086 and 0.902 µg/kg dw, respectively). The antioxidant capacity of the standards was also analysed at the concentrations found in the matrices studied. A significant correlation was found between the concentration of the pure tryptophan standard and the antioxidant capacity (ABTS•+, r2 = 0.891 at p < 0.001 (***); FRAP, r2 = 0.885 at p < 0.01 (**); and ORAC, r2 = 0.854 at p < 0.01 (**)). According to these results, winery by-products can be highlighted as valuable materials to be used as novel ingredients containing tryptophan, serotonin, and melatonin, while tryptophan was identified as the most relevant contributor (out of phenolic compounds) to the antioxidant capacity exhibited by wine by-products.

Inula viscosa (L.) Aiton Ethanolic Extract Inhibits the Growth of Human AGS and A549 Cancer Cell Lines.

The present study shows the chemical profile and cytotoxic properties of the ethanolic extracts of Inula viscosa from Northeast Algeria. The extract was obtained by maceration using ethanol. Its phenolic profile was determined using ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS), which allowed the identification and quantification of 17 compounds, 1,5-O-caffeoylquinic acid being the most abundant. The cytotoxic activity was assessed against human gastric cancer (AGS) and human non-small-cell lung cancer (A549) cell lines, whereas ethanolic extract elicited nearly 60 % and 40 % viability loss toward AGS and A549 cancer cells, respectively. Results also showed that cell death is caspase-independent and confirmed the involvement of RIPK1 and the necroptosis pathway in the toxicity induced by the I. viscosa extract. In addition, the ethanolic extract would not provoke morphological traits in the cancer cells. These findings suggest that I. viscosa can be a source of new antiproliferative drugs or used in preparation plant-derived pharmaceuticals.

Electrospray Mass Spectrometry to Study Combinatorial iClick Reactions and Multiplexed Kinetics of [Ru(N3)(N∧N)(terpy)]PF6 with Alkynes of Different Steric and Electronic Demand.

In a combinatorial approach, a family of ruthenium(II) azido complexes [Ru(N3)(N∧N)(terpy)]PF6 with terpy = 2,2':6',2″-terpyridine and N∧N as a bidentate chelator derived from 2,2'-biypridine and its 4,4'-disubstituted derivatives, 2,2'-bipyrimidine, and 1,10-phenanthroline were reacted with different internal and terminal alkynes to give access to a total of 7 × 7 = 49 triazolato complexes in a room-temperature catalyst-free iClick reaction. The reactants were mixed in a repurposed high-performance liquid chromatography (HPLC) autosampler, and the reaction progress was monitored by direct injection into an electrospray mass spectrometer. The ratio of the peak intensities of [Ru(N3)(N∧N)(terpy)]+ and [Ru(triazolato)(N∧N)(terpy)]+ was converted to a colored heat map for facile visual inspection of the conversion ratio. By automated multiple injections of the reaction mixture in fixed time intervals and plotting peak intensities over reaction time, pseudo-first-order rate constants were easily determined. Finally, nonoverlapping isotope patterns of the azido starting materials and triazolato products enabled multiplexed parallel determination of rate constants for four different ruthenium(II) azido complexes from a single sample vial, thereby reducing experiment time by 75%.

Metabolite Profiling, Antioxidant and Key Enzymes Linked to Hyperglycemia Inhibitory Activities of Satureja hispidula: An Underexplored Species from Algeria.

In the present study, two extracts from the aerial parts of the endemic species Satureja hispidula were analyzed for the first time by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS) method in order to identify and quantify their phenolic compounds. These extracts' antioxidant, α-glucosidase and α-amylase inhibitory activities were also evaluated. UHPLC-DAD-ESI/MS allowed the identification of 28 and 20 compounds in the ethanolic and aqueous extracts, respectively; among them, 5-O-caffeoylquinic acid was the most abundant in both extracts. The biological assay results indicate that the species S. hispidula, besides its high antioxidant power, is also potentially useful for inhibiting the α-glucosidase enzyme. In both antioxidant and α-glucosidase inhibitory assays, the aqueous extract exhibited the most promising results, significantly better than the standards used as positive controls.

Metabolite Profiling of Alocasia gigantea Leaf Extract and Its Potential Anticancer Effect through Autophagy in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a poor-prognosis type of cancer with high resistance to chemotherapy, making the search for safe drugs a mandatory issue. Plant-derived products have potential to reduce negative side effects of cancer treatments. In this work, ability of a defatted methanolic extract of Alocasia gigantea leaves to fight HCC was evaluated in an animal model. Overall, treatment of HCC-induced mice with the methanolic extract at 150 mg/kg body weight for four consecutive weeks caused induction of autophagy through silencing of the relative expression of autophagy suppressor (mTOR) and inducement of autophagy markers (AMPK, Beclin-1, and LC-3). Moreover, it improved preservation of the hepatic histological architecture of the animals, with minor hepatocytic changes but scattered foci of hepatocytic apoptosis. Chemical profiling of the methanolic extract via ultra-high-performance liquid chromatography coupled to a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI-MS/MS) allowed identification of di-C-glycosyl flavones, mostly represented by 6-C-hexosyl-8-C-pentosyl apigenin isomers, which may possibly be associated with inducement of the autophagy pathway in HCC. Overall, these outcomes gave an initial visualization of the operative effect of some compounds in A. gigantea leaves that are potential treatment for HCC.

Chemical Composition and Antioxidant, Anti-Inflammatory, and Enzyme Inhibitory Activities of an Endemic Species from Southern Algeria: Warionia saharae.

Warionia saharae Benth. & Coss. (Asteraceae) is an endemic species of North Africa naturally grown in the southwest of the Algerian Sahara. In the present study, this species’ hydromethanolic leaf extract was investigated for its phenolic profile characterized by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS). Additionally, the chemical composition of W. saharae was analyzed by gas chromatography–mass spectrometry, and its antioxidant potential was assessed through five in vitro tests: DPPH● scavenging activity, ABTS●+ scavenging assay, galvinoxyl scavenging activity, ferric reducing power (FRP), and cupric reducing antioxidant capacity. The UHPLC-DAD-ESI/MS analysis allowed the detection and quantification of 22 compounds, with taxifolin as the dominant compound. The GC–MS analysis allowed the identification of 37 compounds, and the antioxidant activity data indicate that W. saharae extract has a very high capacity to capture radicals due to its richness in compounds with antioxidant capacity. The extract also showed potent α-glucosidase inhibition as well as a good anti-inflammatory activity. However, weak anti-α-amylase and anticholinesterase activities were recorded. Moreover, an in silico docking study was performed to highlight possible interactions between three significant compounds identified in W. saharae extract and α-glucosidase enzyme.

Alkali and Alkaline Earth Metal Ions Complexes with a Partial Peptide of the Selectivity Filter in K+ Channels Studied by a Cold Ion Trap Infrared Spectroscopy.

The infrared (IR) spectra of alkali and alkaline earth metal ion complexes with the Ac-Tyr-NHMe (GYG) peptide have been measured by laser photodissociation in a cold ion trap coupled with an electrospray mass spectrometer. The GYG peptide corresponds to a portion of the ion selectivity filter in the KcsA K+ channel that allows K+ to pass, but blocks Na+ even though it has a smaller ionic radius than K+ . This current study extends a previous investigation on Na+ and K+ to the entire set of alkali metaI ions and alkaline earth dications. IR-IR hole-burning (IR2 dip) spectroscopy has established the coexistence of several conformers of the GYG-metal ion complexes. The structures of the conformers were assigned by comparison between the isomer-selected IR spectra and theoretical IR spectra obtained from quantum chemical calculations. It was found that the structure of the dominant conformer correlates with the ability of the ion to permeate through the K+ channel.

Microfluidic Flow-through SPME Chip for Online Separation and MS Detection of Multiple Analyses in Complex Matrix.

Simplifying tedious sample preparation procedures to improve analysis efficiency is a major challenge in contemporary analytical chemistry. Solid phase microextraction (SPME), a technology developed for rapid sample pretreatment, has flexibility in design, geometry, and calibration strategies, which makes it a useful tool in a variety of fields, especially environmental and life sciences. Therefore, it is important to study the coupling between the microfluidic electrospray ionization (ESI) chip integrated with the solid phase microextraction (SPME) module and the electrospray mass spectrometer (MS). In our previous work, we designed a solid phase microextraction (SPME) module on a microfluidic chip through geometric design. However, automation and calibration methods for the extraction process remain unresolved in the SPME on-chip domain, which will lead to faster and more accurate results. This paper discusses the necessity to design a micromixer structure that can produce different elution conditions on the microfluidic chip. By calculating the channel resistances, the microfluidic chip’s integrated module with the micromixer, SPME, and ESI emitters optimize the geometry structure. We propose the annular channel for SPME to perform the resistances balance of the entire chip. Finally, for SPME on a single chip, this work provides a quantitation calibration method to describe the distribution of the analytes between the sample and the extraction phase before reaching the adsorption equilibrium.

Automated and enhanced extraction of a small molecule-drug conjugate using an enzyme-inhibitor interaction based SPME tool followed by direct analysis by ESI-MS.

We report a novel, fast, and automatic SPME-based method capable of extracting a small molecule-drug conjugate (SMDC) from biological matrices. Our method relies on the extraction of the drug conjugate followed by direct elution into an electrospray mass spectrometer (ESI-MS) source for qualitative and quantitative analysis. We designed a tool for extracting the targeting head of a recently synthesized SMDC, which includes acetazolamide (AAZ) as high-affinity ligand specific to carbonic anhydrase IX. Specificity of the extraction was achieved through systematic optimization. The design of the extraction tool is based on noncovalent and reversible interaction between AAZ and CAII that is immobilized on the SPME extraction phase. Using this approach, we showed a 330% rise in extracted AAZ signal intensity compared to a control, which was performed in the absence of CAII. A linear dynamic range from 1.2 to 25μg/ml was found. The limits of detection (LOD) of extracted AAZ from phosphate-buffered saline (PBS) and human plasma were 0.4 and 1.2μg/ml, respectively. This with a relative standard deviation of less than 14% (n = 40) covers the therapeutic range. Graphical abstract.

Differentiation of Phenolic Composition Among Tunisian Thymus algeriensis Boiss. et Reut. (Lamiaceae) Populations: Correlation to Bioactive Activities.

Twelve Tunisian Thymus algeriensis populations growing wild in different bioclimatic zones, extending from the subhumid to the upper-arid bioclimates, were compared regarding their phenolic composition and their ability to serve as antioxidant, anti-acetylcholinesterase, and antibacterial agents. A significant variation of phenol profile was observed between the analyzed populations, as assessed by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MSn) technique. Rosmarinic acid was the main phenolic compound in most populations (383.8–1157.8 µg/mL extract), but still, those from the upper-arid bioclimatic zone were distinguished by the presence of carvacrol (1374.7 and 2221.6 µg/mL extract), which was absent in the remaining ones. T. algeriensis methanolic extracts were found to possess a substantial antioxidant and anti-acetylcholinesterase activities, with significant variation observed between populations, which were correlated to their phenolic contents. The antibacterial activity of the extracts tested against seven bacteria was revealed only by populations collected from upper-arid bioclimate and mainly associated with the presence of carvacrol. Extracts revealed a bacteriostatic effect against all bacteria (MIC = 1.4 mg/mL). Yet, the bactericidal activity (MBC = 1.4mg/mL) was restricted to the gram-negative bacteria Escherchia coli.

Mass-Spectrometric Observation of C+ Ions during Electrospray with In-Source Atomization

Carbon C+ ions formed in a mass-spectrometric electrospray source with controlled in-source fragmentation and atomization interface have been observed for the first time. The measurements were performed in a special MI-20 LowMass mass spectrometer (MS-Bio LLC) using aqueous methanol solutions of lithium and beryllium salts. The peak of C+ ions was substantially broadened as compared to the peaks of metal ions. A model is proposed that explains the formation of C+ ions due to charge exchange immediately at the high-vacuum boundary near the skimmer output.

The electrochemical profiles of Auranofin and Aubipyc, two representative medicinal gold compounds: A comparative study

A micro-electrochemical reaction cell was coupled to an electrospray mass spectrometer in order to track redox transformations for two representative medicinal gold compounds - i.e. [(2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S)(triethylphosphine)gold(I)] and [Au(bipydmb-H)(OH)][PF6] (where bipydmb-H is deprotonated 6-(1,1-dimethylbenzyl)-2,2′-bipyridine), known as Auranofin and Aubipyc respectively - in parallel to square wave voltammetry (SWV) measurements. Irreversible oxidation of thio-glucose tetraacetate was the dominant reaction for the gold(I) compound Auranofin; oxidation was accompanied by hydrolysis leading to progressive deacetylation. Two main active forms were identified for this prodrug: the triethylphosphinegold(I) cation and a gold(I) thioglucose species, with a variable number of acetyl groups. For the gold(III) complex Aubipyc irreversible reduction of the gold(III) center was highlighted, accompanied by a ligand exchange process. The free gold(I) ion is proposed to be the final species that subsequently binds transport proteins in the bloodstream. Molecule specific mass spectrometry determinations provide complementary data to square wave voltammetry helping to understand the nature of the electrochemical conversions of complex or unstable compounds. Finally, it was possible to establish that oxidizing conditions during drug preparation and administration should be avoided in the case of Auranofin; conversely, reduction conditions typical for the blood or the cytosol environment are suitable to obtain the active gold(I) species from the gold(III) complex Aubipyc.

Evaluation of anti-onchocercal activity of pseudopalmatine, a quaternary protoberberine alkaloid of Enantia chlorantha (Syn. &lt;i&gt;Annickia chlorantha&lt;/i&gt;)

As part of our efforts towards identifying and subsequently developing lead compounds from medicinal plants of Cameroon to combat neglected tropical diseases, we embarked to phytochemically investigate Enantia chlorantha (Syn. Annickia chlorantha). The rationale for choosing this plant is its numerous uses in folk medicine in Cameroon and other parts of Africa. In Cameroon the quaternary protoberberine alkaloids, columbamine (2), palmatine (3) and jatrorrizine (4) have been isolated from the stem back and combined to produce a phytomedicine (HEPAZOR®) used in the treatment of viral hepatitis. An alkaloidal extraction of the methanolic extract of the stem bark of the plant was carried-out and this afforded yellow amorphous solids whose structure was obtained using routine nuclear magnetic resonance spectroscopy (NMR), high pressure liquid chromatography coupled to an electrospray mass spectrometer (HPLC-ESI-MS) and comparison with literature. The compound was identified as pseudopalmatine (1), a quaternary protoberberine alkaloid. Preliminary screening of the compound on both adult and juvenile worms of Onchocerca ochengi, a close relative of Onchocerca volvulus, the parasite responsible for human onchocerciasis (river blindness), showed that compound (1) was inactive at a concentration of 500 μg/mL on the adult worms, but inhibited microfilariae motility completely at this same concentration and by 50 % at 250 μg/mL and was thus considered active. While this work to the best of our knowledge constitutes the first report on the anti-onchocercal activity of quaternary protoberberine alkaloids in general and pseudopalmatine (1) in particular isolated from E. Chlorantha, it has however opened a window for further investigation of the anti-onchoceral activity of this class of compounds. Key words: anti-onchocercal, pseudopalmatine, alkaloid, Enantia chlorantha

Масс-спектрометрическое наблюдение иона С-=SUP=-+-=/SUP=- при электрораспылении с атомизацией в источнике

AbstractCarbon C^+ ions formed in a mass-spectrometric electrospray source with controlled in-source fragmentation and atomization interface have been observed for the first time. The measurements were performed in a special MI-20 LowMass mass spectrometer (MS-Bio LLC) using aqueous methanol solutions of lithium and beryllium salts. The peak of C^+ ions was substantially broadened as compared to the peaks of metal ions. A model is proposed that explains the formation of C^+ ions due to charge exchange immediately at the high-vacuum boundary near the skimmer output.

Trace Phosphate Improves ZIC-pHILIC Peak Shape, Sensitivity, and Coverage for Untargeted Metabolomics.

Existing hydrophilic interaction liquid chromatography (HILIC) methods, considered individually, each exhibit poor chromatographic performance for a substantial fraction of polar metabolites. In addition to limiting metabolome coverage, such deficiencies also complicate automated data processing. Here we show that some of these analytical challenges can be addressed for the ZIC-pHILIC, a zwitterionic stationary phase commonly used in metabolomics, with the addition of trace levels of phosphate. Specifically, micromolar phosphate extended metabolome coverage by hundreds of credentialed features, improved peak shapes, and reduced peak-detection errors during informatic processing. Although the addition of high levels of phosphate (millimolar) as a HILIC mobile phase buffer has been explored previously, such concentrations interfere with mass spectrometric (MS) detection. We show that using phosphate as a trace additive at micromolar concentrations improves analysis by electrospray MS, increasing signal for a diverse set of polar standards. Given the small amount of phosphate needed, comparable chromatographic improvements were also achieved by direct addition of phosphate to the sample during reconstitution. Our results suggest that defects in ZIC-pHILIC performance are predominantly driven by electrostatic interactions, which can be modulated by phosphate. These findings constitute both a methodological improvement for untargeted metabolomics and an advance in our understanding of the mechanisms limiting HILIC coverage.

Peculiarities of the Mass Spectrometric Detection of Anthocyanins in High-Performance Liquid Chromatography

The dependence of the degree of fragmentation of anthocyanin “molecular” ions on the cone voltage of a mass spectrometric electrospray ionization detector was studied. It was found that the voltage required for the fragmentation of 50% of original “molecular” ions, E f (0.5), increased with the number of glycoside residues. The fragmentation of glycosides proceeds with the removal of the entire residue regardless of their structures. In the case of 3,5-diglycosides, two types of fragment ions formed due to the loss of glycosidic residues from different positions; the ratio of their peak intensities is reciprocal to the ratio of the masses of residues eliminated. The values of E f (0.5) for monoglycosides (190 V), diglycosides (229 V), triglycosides (267 V), and for some acylated cyanidin-3,5-diglycosides are determined. These results were given for the gradient separation of anthocyanins by reversed-phase HPLC in aqueous acetonitrile containing 10 vol % of formic acid using quadrupole mass spectrometric detection.

Optimization and validation of reverse phase HPLC method for qualitative and quantitative assessment of polyphenols in seaweed

A simple reverse phase-high performance liquid chromatography (RP–HPLC) coupled to a diode array detector (DAD) and negative ion electrospray mass spectrometer (ESI–MS) method was developed for simultaneous identification and quantification of phenolic antioxidants in seaweed. The proposed method was validated in terms of linearity, limits of detection (LOD), limits of quantification (LOQ), recovery and intermediate precision. The calibration curves were linear with correlation coefficient ranging from 0.9909 to 0.9997 while the values of LOD (0.26–0.82mg/L), LOQ (0.77–2.50mg/L), recovery (≥97.2%) and precision in terms of retention time (%RSD ≤2.27) and peak area (% RSD ≤5.11) were satisfactory. Brown seaweed Himanthalia elongata used in this study was extracted with 60% methanol and the crude extract was cleaned with SPE (Solid Phase Extraction) cartridge. HPLC-DAD-MS/MS analysis of the SPE fraction allowed the identification of 7 phenolic compounds comprising phlorotannins, hydroxybenzoic acid, hydroxycinnamic acid and flavonols subclasses of polyphenols. Quantitative analysis of these compounds revealed the presence of phloroglucinol (394.1±4.33μg/g), gallic acid (96.3±3.12μg/g), chlorogenic acid (38.8±1.94μg/g), caffeic acid (44.4±2.72μg/g), ferulic acid (17.6±0.85μg/g), myricetin (8.6±0.85μg/g) and quercetin (4.2±0.15μg/g), in the extract. The SPE fraction were tested for antioxidant capacity which were significantly (P <0.05) higher (EC50; 14.5±0.57mg/g) than the ascorbic acid (EC50; 35.8±0.59mg/g) and the crude extract (EC50; 46.3±0.48mg/g). The occurrence of all these phenolic antioxidant compounds in H. elongata extract suggested that the developed method is sensitive enough and reproducible and could be used for qualitative and quantitative assessment of polyphenols in seaweed.